When you think of the Nats starting pitching you do tend to forget Edwin Jackson. Obviously Strasburg is the first name that comes to mind, followed by Gio and the year he's having. ZNN is probably next given he's the only one that pitched last year, was good then, and is good now. Then maybe you think of Jackson, but probably you thought of Detwiler early on with his great start, then nobody, and now you're thinking about Chien Ming Wang.'
I'm not saying this is necessarily unfair to Jackson. He's less talented than the Top 3, older than everyone, and the only one not guaranteed to be here next year. He started slow, and he has only 1 win. Still... he's you could argue* he's been the Nats second best starter this season. He's 2nd to Gio in WHIP and H/9, 2nd to ZNN in BB/9, 3rd in K behind Strasburg and Gio (yes 3rd out of 5 isn't a big deal, but Gio and Stras are fighting over the league lead). It's his best season ever, so far. According to pitching WAR he's been the 18th most valuable starter in the NL. You can believe in the ranking of that number as much as you want but it nails what all the other stats say too. He's pitched like a #2 guy out of the #4 slot.
But that factoid - that he's in the #4 slot - is what makes makes his signing here a mistatke. Not by Rizzo but by Boras. You only sign a one-year deal at age 28 if you want to use that one-year as a springboard to something bigger. That elusive long-term, big-money deal that all players want. But to justify that to the fans and to the owners you need more than fancy stats. You need results. You need wins - as many, in as big as situations as possible.
The "many" part is a problem, because of the offense behind Edwin. The Nationals line-up is low-scoring, you can't deny that. It may improve in the future, but for a good 3rd of the season it'll be in the bottom of the NL and it's not likely to jump above average at any point in the year. Those type of offenses create games where wins and losses are decided almost at random, and often late in the games. If you can't just shut a team down (like Gio and Stras can) you can easily end up with a well-pitched loss. The Nats are tied for 4th in wins in the majors, but have only 2 pitchers with 4+ wins. The other three teams have at least 3. Edwin has been on the receiving end of some poor luck when it comes to this and has only 1. His luck could turn but then again, it could not.
The "big situation" could also be part of the problem. As the 4th guy in the rotation, who's to say what his role will be come playoff time? Certainly Strasburg and Gio will go 1, 2 (assuming Strasburg's arm is ok to do it). That next game feels much more likely to go to ZNN than Edwin. ZNN might not have as good stats as Edwin this year, but he's almost as good (and might be better come year's end), he's shown he's more capable of pitching that plus-level game (he's more little girl with the curl to EJax's "Steady Eddie"), and he's the guy you are going to want to keep happy since he's coming back. That leaves Edwin in the 4th spot, but if the Nats fall down 2-1 in the playoffs, are you going to really going to go with Edwin over Gio or Strasburg again? (OK probably over Strasburg again - if you are pitching him at that point you are going to be very arm aware)
Suddenly Boras is trying to sell a guy with a 9-12 record who was left out of a playoff rotation as a guy worth a big mutli-year deal? Good luck with that. We'll see what happens - maybe Strasburg does shut down and Edwin wins a playoff MVP. Or maybe he reverts to pitching like the last few years, continues to get no support and is a 4.00 ERA pitcher with a 6-14 record looking for a 5 year 100 million dollar deal. Whatever happens this isn't a Nats problem. They are golden to have Edwin pitch like this out of the #4 slot, but depending on what they actually turned down it looks like it might be a misstep by the Boars regime that could cost his client millions.
* You could. I personally would still argue Strasburg is the 2nd best (and pretty easily so) but the argument could be made.